It was a banner year for research in invisibility. The U.S. army could have a device within a decade.

Fitting, then, that the science of invisibility – yes, that's correct – made a giant leap forward in 2008.

Think Harry Potter sneaking out of Hogwarts unseeable in his "cloak of invisibility." Or, more to the point, the invisible Romulan ship chased by the USS Enterprise in the original sci-fi Star Trek series, the fount of so many subsequent real-life inventions.

This summer, researchers at the University of California, Berkeley, demonstrated for the first time the ability to "cloak" three-dimensional objects in artificially engineered "meta-materials" that bent light around the objects. They "disappeared." Previous efforts were able to bend microwaves around objects, but visible light has proved much more difficult. This differs from the stealth technology developed in the 1980s, which reduces radar's ability to pick up a fighter jet, making it hard to track, but doesn't render the jet invisible. "Cloaking" would bypass the radar or other waves around the plane as if it weren't there.

The meta-materials are made using nanotechnology and engineered out of artificial atoms that are smaller than the wavelengths of light itself. One Berkeley approach used a "fishnet" material of metal layers to reverse the direction of light; the other used tiny nanowires made of silver.

"You'd have to wrap whatever you wanted to cloak in the material," said researcher Jason Valentine. "By sending light around the object that is cloaked, you don't see it."

Humans are able to see objects because they scatter the light that strikes them, reflecting some of it back to the eye. Sometimes there is "negative refraction," the effect that distorts what's being seen: a straw placed in water appears bent, a fish slightly further ahead of where it actually is.

But the negative refraction capacity of meta-materials is somewhat different. Instead of a bent straw or the fish looking slightly ahead of itself, "it would actually appear to be above the water's surface," Valentine explained, adding by way of understatement: "It's kind of weird."

This week, scientists at Purdue University in Indiana announced another breakthrough in cloaking technology, called transformation optics, in the journal Science.

The new way of "manipulating and controlling light at all distances represents a new paradigm for the science of light," said the lead researcher, Vladimir Shalaev, an electrical and computer engineer.

The mathematics behind transformation optics are similar to the mathematics behind Einstein's theory of general relativity, which describes how gravity warps space and time. "Whereas relativity demonstrates the curved nature of space and time, we are able to curve space for light," said Shalaev, "and we can design and engineer tiny devices to do this."

Instead of a straw or fish, Shalaev used a stone to help explain the science to ordinary, still-visible people: "An electromagnetic cloak could bend light around itself, similar to the flow of water around a stone, making invisible both the cloak and an object hidden inside."

His team used a device resembling a round hairbrush, an array of tiny needles radiating out from a central spoke that bent light around an object. The needles are so small they reduced refraction or distortion of the light to almost zero, rendering the object invisible to a viewer.

Before anyone begins, however, to plan next year's Halloween costume, consider that Purdue's research, like Berkeley's, is funded by the U.S. Army Research Office.

As well, the infamous DARPA (Defence Advanced Research Agency) – sponsor of work on remote-controlled cyber-insect soldiers and equipment-carrying robots called BigDog– is also interested in coating experiments. It specifically wants a device to make objects invisible to radar and radio waves, not just human eyes.

During a teleconference this week, the Army's Dr. Richard Hammond said the Pentagon's goal is to develop an invisibility coating that will make tanks, airplanes, buildings – and, eventually down the road, even people – "disappear." It hopes to have a meta-materials device in production within the next two or three years, assuming full-scale cloaking isn't prohibitively expensive, which it well may be.

One of the pioneers of invisibility work earlier in the decade, Britain's John Pendry, an eminent theoretical physicist at London's Imperial College, marvels at the meta-materials' potential.

"You could build a shed out of this material and drive a tank in there, or hold a party inside it, and once you close the door everything it contains would be completely invisible," he recently said.

As well as curving light to make an object apparently disappear, the opposite effect can also be produced. Light can be concentrated in one specific area, making sunlight collection more efficient in solar energy applications.

Researchers say the technology will allow computers and consumer electronics to use light instead of electronic signals to process information. Ultra-powerful microscopes, 10 times stronger than exist today, will be able to see germs, chemical agents, even DNA.

But that's not all that happened in the year of the unseen. How about the unheard?

In June, Spanish scientists developed the blueprint for an "acoustic cloak," or shield, which would make objects impervious to sound by channelling sound waves around them. The technology could be used to, among other things, build soundproof homes and acoustically advanced concert halls. And once again, the military might be interested, both in concealing submarines from sonar detection and creating a new class of stealth ships.

But the material may need to be perfected first, pioneer Pendry pointed out. "You don't want to wrap a submarine in something that is heavy and several inches thick. It would add quite a lot to the Navy's fuel bill, I think."

Lynda Hurst is a feature writer at the Toronto Star. She can be reached at lhurst@thestar.ca

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